/**
 * @file STL_MD5.h
 * @author Derek Liu (yjkhtddx@sina.com)
 * @brief 
 * @version 0.1
 * @date 2020-09-10
 * 
 * @copyright Copyright Sci-Tech Laboratories (c) 2020
 * 
 */

#ifndef __STL_MD5_H__
#define __STL_MD5_H__

#include <string>
#include <iostream>

namespace STL
{

  // a small class for calculating MD5 hashes of strings or byte arrays
  // it is not meant to be fast or secure
  //
  // usage: 1) feed it blocks of uchars with update()
  //      2) finalize()
  //      3) get hexdigest() string
  //      or
  //      MD5(std::string).hexdigest()
  //
  // assumes that char is 8 bit and int is 32 bit

  class MD5
  {
  public:
    typedef unsigned int size_type; // must be 32bit

    MD5();
    MD5(const std::string &text);
    void update(const unsigned char *buf, size_type length);
    void update(const char *buf, size_type length);
    MD5 &finalize();
    std::string hexdigest() const;
    std::string hexUpperDigest() const;
    std::string hexLowerDigest() const;
    std::string binaryDigest() const;
    friend std::ostream &operator<<(std::ostream &, MD5 md5);

  private:
    void init();
    typedef unsigned char uint1; //  8bit
    typedef unsigned int uint4;  // 32bit
    enum
    {
      blocksize = 64
    }; // VC6 won't eat a const static int here

    void transform(const uint1 block[blocksize]);
    static void decode(uint4 output[], const uint1 input[], size_type len);
    static void encode(uint1 output[], const uint4 input[], size_type len);

    bool finalized;
    uint1 buffer[blocksize]; // bytes that didn't fit in last 64 byte chunk
    uint4 count[2];          // 64bit counter for number of bits (lo, hi)
    uint4 state[4];          // digest so far
    uint1 digest[16];        // the result

    // low level logic operations
    static inline uint4 F(uint4 x, uint4 y, uint4 z);
    static inline uint4 G(uint4 x, uint4 y, uint4 z);
    static inline uint4 H(uint4 x, uint4 y, uint4 z);
    static inline uint4 I(uint4 x, uint4 y, uint4 z);
    static inline uint4 rotate_left(uint4 x, int n);
    static inline void FF(uint4 &a, uint4 b, uint4 c, uint4 d, uint4 x, uint4 s, uint4 ac);
    static inline void GG(uint4 &a, uint4 b, uint4 c, uint4 d, uint4 x, uint4 s, uint4 ac);
    static inline void HH(uint4 &a, uint4 b, uint4 c, uint4 d, uint4 x, uint4 s, uint4 ac);
    static inline void II(uint4 &a, uint4 b, uint4 c, uint4 d, uint4 x, uint4 s, uint4 ac);
  };

  std::string md5(const std::string str);
  std::string md5_upper(const std::string str);
  std::string md5_lower(const std::string str);
  std::string md5_binary(const std::string str);

} // namespace STL

#endif //__STL_MD5_H__
